The purpose of this project is to understand the impact of different types of best friendship dissolution on children's psychological well-being. While it is well-established that consistent friendship involvement promotes emotional health and psychosocial adjustment, little is known about the impact of changes in children's friendship involvement, such as when children's friendships are dissolved or disrupted. If estimates are correct, nearly half of all friendships are disrupted over the course of one school year during late childhood. Recent findings indicate that children who lose friendships are at increased risk for psychological distress, and that children who lose friendships and are not able to replace them experience significantly greater victimization and loneliness. Thus, friendship dissolutions represent common yet understudied risk factors that may pose significant dangers for many children. Accordingly, the first aim of this project is to examine the extent to which different types of best friendship dissolution occur in late childhood. Two different types of dissolution may be: (1) complete dissolution, where children no longer relate as friends at all, and (2) downgrade dissolutions, where children continue to share a friendship but are no longer best friends. The second specific aim is to assess the relations between friendship dissolution and children's psychological health. Specifically, the project will evaluate the associations between two different types of best friendship dissolution and self-reports of psychosocial distress (e.g., loneliness, depression) and internalizing and externalizing emotions (sadness and anger). 300 children (150 girls) from middle-schools in the suburban Buffalo, New York area will complete questionnaires in their classrooms at three time points throughout the 6th grade year and one time point after they transition into the 7th grade. This project will employ a four time-point longitudinal design to permit evaluation of the impact of short-term friendship dissolution (e.g., when a friendship dissolves but is followed by friendship replacement), and repeated/long-term friendship dissolution (e.g., when a friendship dissolves and is replaced, but the latter friendship also dissolves). Questionnaire data will also assess the ways in which children evaluate or think about friendship dissolution. Analyzing children's cognitions may be useful in understanding individual differences in the psychological concomitants of dissolution. Throughout the study, a special emphasis will be placed on individual child characteristics, such as sex and behavioral profile (e.g., aggressive), which may make children more vulnerable to dissolution and associated negative consequences. The long-term goal of this project is to contribute to the advancement of knowledge about peer difficulties at the dyadic level and their relation to psychological well-being. Applications of this project might include educating school and childcare professionals about the warning signs, risks, and adverse mental health and adjustment consequences of friendship dissolution and disturbance, and improving interventions designed to address psychosocial maladjustment and peer relationship difficulties.